Reforestation is desirable for many reasons and is generally required by statute following the logging of forested areas. Such reforestation requires that seedlings be planted to provide forest regrowth for environmental and economic reasons.
The survival and subsequent growth rate of planted seedlings, however, is heavily dependent on the conditions under which such seedlings are planted and nurtured. If a reforestation site has poor drainage and cool soil temperatures, it is beneficial to provide the seedlings with better growing conditions such as enhanced drainage, warmer soil temperatures, increased access to nutrients and decreased competition from surrounding vegetation.
The use of mounds in which to plant seedlings is known to increase their growth rate. The method of construction of such mounds, however, is important. For example, it may be desirable to invert the "duff cover" which comprises the nitrogen rich litter, fermentation and humus soil layers of the forest floor so as to make the duff cover accessible for the sensitive seedling roots. The duff cover will be buried under the mineral soil covering which forms the top of the mound. The mineral soil will facilitate warming by the sun and generally lead to increased soil temperatures in the mound. If the depth of the mineral soil is sufficient, it also assists in controlling the growth of competing vegetation surrounding the seedling. The elevated planting position is beneficial on wet sites. A mineral soil mound, without inverted "duff cover", may be desirable on some sites, and can be created by removing the duff cover before mounding.
Previously, mounds have been machine constructed in a process called "spot mounding" using apparatuses called "spot mounders" but some such techniques have often been less than satisfactory. In one machine used for site preparation, for example, two sets of scarifying wheels are used which continuously rotate and which are attached to a frame pivotally attached to and towed behind a prime mover such as a tractor or crawler. A braking system slows the rotation of the scarifying wheels when it is desired to form the mounds used for seedling planting. While the device operates satisfactorily in some soil conditions, it does not operate well in all soil conditions. This is so because the scarifying wheels are not driven into the ground nor is the towed frame heavy enough to give the required depth to the digging elements in heavy compacted soil or thick duff layer conditions.